Confirmed: Google AdSense Ads User Interface Tests

Yesterday a Google AdSense publisher posted a thread at WebmasterWorld complaining that his AdSense ads are appearing in different ad style variations.

Shortly after he posted his complaint, an official Google representative confirmed the changes. Google said:

The variation you noticed is part of normal and ongoing testing we perform to improve our ad formats. They only run for a very short amount of time and are only shown to a very small percentage of your users.

Our engineers are always closely monitoring the results of our test, and any variations should impact only a small percentage of your impressions.

What were the tests? Well, I do not have pictures, but this is how the AdSense publisher described it.